BACKGROUND: This study aimed to examine surgical trends in knee arthroplasty over past 18 years and identify the factors associated with risk of revision surgeries following total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) in South Korea. METHODS: This study was conducted using National Health Insurance Service - National Sample Cohort database, approximately 1 million individuals from 2002 to 2019. We analyzed general trends and procedural rates of knee arthroplasty, stratified by age, location of residence, and hospital size. Additionally, we investigated the risk factors of knee arthroplasty failure in UKA and TKA. RESULTS: The average age of the 15,395 individuals who underwent UKA (n = 664) or TKA (n = 14,731) was 69.8 years (standard deviation 7.2), and 77.3% were women. In TKA, occurrence increased by approximately 4.9 times from 2002 to 2010 and by 1.5 times 2010 onward. In contrast, the number of UKA procedures did not increase until 2008, after which it increased 6.1-fold by 2019. An increasing trend in TKA procedures was observed among individuals aged 70-79 and >
80 years, whereas the UKA procedural rates increased across all age groups. The revision rate was higher in UKA than that in TKA (13.7% vs. 2.8%). The risk factors were younger age, diabetes mellitus for TKA, and osteoporosis for UKA. CONCLUSION: Unlike that of TKA, procedural rate increment of UKA occurred in younger people recently and featured a considerably higher revision rate. Given that UKA has a higher revision rate and different risk factors than TKA, monitoring should be tailored specifically for each procedure.